1. Field of the Invention
This invention pertains to an apparatus and method for separating gas components by a gas fractionalization system, and, more particularly, to the regulation of the work done by a compressor by manipulating the air flow through the compressor depending on the quantity of consumable gas requested by an end user.
2. Description of the Related Art
Gas fractionalization systems are used for separating a desired gas from a gas mixture, such as air, and delivering the separated gas to an end user. A typical gas fractionalization system is an oxygen concentrator, which separates the oxygen from air, for subsequent inhalation by a patient. An oxygen concentrator, or similar pressure swing absorption system, typically includes molecular sieve beds for separating the gas into an oxygen and a nitrogen fraction. The oxygen is subsequently provided to the patient while the nitrogen is retained in the sieve bed and subsequently purged. Generally, in a pressure swing absorption system, two sieve beds are utilized. One sieve bed separates nitrogen from the oxygen while the other sieve bed is simultaneously being purged of the nitrogen previously absorbed during the prior fractionalization cycle.
Typically, an oxygen concentrator utilizes a compressor that draws air from the ambient environment and presents compressed air to the molecular sieves pressurizing the sieves for fractionalization of the gases. The concentrated gas then enters a product chamber. A flow metering device is located between the product chamber and the patient. The user manipulates the flow metering device to present a desired amount of oxygen to the patient. Typically, an oxygen concentrator can provide a flow of oxygen ranging from 1 liter per minute to 5 liters per minute. The amount of oxygen delivered to a patient is prescribed by a physician and may vary depending on the physical condition of the patient. A typical oxygen concentrator is illustrated in U.S. Pat. No. 5,183,483 the contents of which are incorporated herein by reference.
Even though oxygen concentrators are designed to provide an oxygen flow rate between 1 to 5 liters per minute, these concentrators usually operate at less than full capacity and typically are operated to provide only 2 liters of oxygen per minute, as generally prescribed. While these oxygen concentrators may provide various flow outputs of oxygen, such systems are generally not designed to provide a varying input flow of air into the molecular sieves. Accordingly, the compressors of these systems continuously operate at one level which produces the maximum flow of oxygen. This results in the compressor needlessly working harder than required to produce the desired flow of oxygen if the flow selected by the patient is less than the maximum output of the gas fractionalization system. The drawbacks of the compressor working harder than necessary are that the compressor at full capacity is noisier than required and also utilizes more power than required. Furthermore, the compressor operates at a higher temperature, increasing the wear of the compressor components. Thus, it is desirable to reduce the work of the compressor when the desired flow rate of the oxygen concentrator is less than the maximum flow rate.
U.S. Pat. No. 5,474,595 discloses an oxygen concentrator system utilizing a compressor having a manually operated valve for reducing air flow into the compressor when the flow output of the oxygen concentrator is less than the maximum output. This patent discloses a two position valve enabling air flow at either a high capacity rate or a low capacity rate depending on the usage by the patient. This valve is manually operated and requires the attendance of a technician to set the valve to the proper position depending on the usage of the concentrator.
U.S. Pat. No. 4,561,287 discloses an oxygen concentrator system that automatically controls the timing cycle for charging the molecular sieve beds by monitoring the pressure levels within the product chamber to determine patient utilization. While this system is suitable for its intended purpose, it functions by manipulating a valve downstream of the compressor for charging the molecular sieve beds and, therefore, does not directly reduce the air mass flow through the compressor.
Accordingly, it is an object of the present invention to provide a pressure swing absorption system wherein the operation of the compressor is modified to correlate the air mass flow through the compressor automatically to correspond with the desired output of the product gas, which results in a reduction in the work done by the compressor.
Furthermore, it is an object of the present invention to provide a gas fractionalization system wherein control of the gas into the compressor is performed based on a parameter indicative of the flow rate of the product gas, thereby requiring less power and providing a more tranquil operating environment.
These objects are accomplished according to the principles of the invention by providing a gas fractional system and method for gas fractionalization having improved efficiency. The gas fractionalization system includes a compressor having an inlet for receiving air from the ambient environment. The system also includes a sensor for sensing a parameter indicative of the flow of concentrated gas delivered from the gas fractionalization system to a patient. A multi-positional valve is disposed in line with the compressor for regulating the flow of air from the ambient environment into the compressor. A valve control manipulates the position of the multi-positional valve depending on the value of the parameter sensed by the sensor for regulating the quantity of air received from the ambient environment into the compressor inlet.
A method for controlling airflow in a gas fractionalization system that achieves the above objects includes the steps of 1) providing a multi-positional valve inline with an inlet of a compressor to control a flow of air from an ambient atmosphere into the inlet, 2) producing concentrated gas from pressurized gas generated by the compressor and delivering a flow of the concentrated gas to a patient, 3) monitoring a parameter indicative of an amount of concentrated gas delivered to such a patient, and 4) controlling the multi-positional valve based on the parameter indicative of the flow of concentrated gas delivered to such a patient so as to regulate the flow of air from an ambient atmosphere into the inlet of the compressor based on the parameter.
These and other objects, features and characteristics of the present invention, as well as the methods of operation and functions of the related elements of structure and the combination of parts and economies of manufacture, will become more apparent upon consideration of the following description and the appended claims with reference to the accompanying drawings, all of which form a part of this specification, wherein like reference numerals designate corresponding parts in the various figures. It is to be expressly understood, however, that the drawings are for the purpose of illustration and description only and are not intended as a definition of the limits of the invention.